High elongation yarn



Jan. 9, 1951 A. J. MEHLER, JR I 2,537,312

HIGH ELONGATION YARN Filed March 17, 1948 IN VEN TOR.

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ATTORNEY Patented Jan. 9, 1951 2,537,312 men ELoNGA'r'IoNYAnN Albert J. Mehler, Jr., New Hope, Va., assignor to 1 E. L du Porit deNemours & Company, Wilmin'gton, Del.,.a corporation of Delaware Application March 17, 1948, Serial No. 15,332

'3 Claims. (01. 18-54) U. S. 2,086,7l9describes the production, fromsm lutions of cellulose acetate having viscosities of less than'100 poises at the extrusion temperature, of yarn having dry elongations of about 30% to 40% by stretching the yarn during spinning 'at a stretchratio not exceeding 2. While yarns prepared by this method have attractive properties, the required slow rate of spinning at 100 meters per minute or thereabout makes the process' unattractive for commercial operation. Attempts to spin at substantially higher spinnin speeds, such as several hundred meters per minute or more, while'rnaintaining high elongation yarn properties, have until now been unsuccessful.

Accordingly, it is an object of this invention to furnish filaments and yarns of cellulose acetate having dry elongations about 35% and spun at wind-up speeds in excess of 500 yards per minute. A further object resides in a process for forming continuous filament yarns of cellulose acetate having elongations above 35% and capable of'being heat-stretched'at relatively 'low'stretch ratio to produce yarns having, after stretching, tensile strengths 'of 2 grams per denier or more and elongations of to Other objects will appear hereinafter.

These objects are accomplished by spinning cellulose acetate solutions of relatively high viscosities and preheated to a relatively high temperature into an evaporative atmosphere through relatively small spinneret orifices and under conditions to give a jet velocity of over 600 yards per minute and a stretch ratio of about 0.85 computed on the basis of the spinning wind-up speed divided by the jet velocity of the filament-forming stream issuing from the spinneret assuming no increase or decrease in diameter upon extrusion. For this, the rate of wind-up is greater than 500 yards per minute but is always less than the rate of extrusion. The solution temperature should be at 75 C. to 85 C., being materially higher than the 60 0. head solution temperature normally used.

The present invention will be more easily under- Example Cellulose acetate prepared from cotton linters and with a degree of polymerization of about 365 2 and a solution viscosity measured at 25% concentration at 40 C. of from 300 to 400 poises was dissolved in acetone-to give a solution composed of 25% cellulose acetate, 72.5% acetone and 2.5% water. After deaerating and filtering in the usual manner, the solution was preheated to to 82 C., at which temperature it was extruded through a spinneret having 43 holes, each hole being 0.04 mm. in diameter, into an evaporative spinning cell of the type described in U. S. Pat- 'ent 1,918,816. The air' entering the cell near the spinneret was at 36 C. and became heated to about C. at the point of aspiration near the bottom of the cell at which point it contained about 60 grams of acetone vapor per cubic meter. The rate of spinning solution delivery was maintained at 3'7 grams per minute equal to a jet velocity of about 700 yards per minute so that the resulting yarn, after separating into two equal parts, measured '75 denier each when wound up at 608 yards per minute. These conditions give a stretchv ratio of 0.85 as defined above. A finish was applied to the yarn during Wind-up and subsequently the yarn was twisted and wound into a suitable shipping package. The finished yarn had the following properties: 1.28 grams per denier dry tenacity; 37.4% dry elongation; 0.83 grams per denier wet tenacity; and 51.6% wet elongation. The yarn showed a more highly crenulated crosssection than yarns spun heretofore at this high wind-up speed.

It is to be noted that a number of factors have been advantageously combined to produce superior yarn. If the relatively high viscosity solution is spun at normal temperatures of solution extrusion but with all the other factors as above described, yarns of markedly lower elongation result. While it is possible to secure even higher elongations by using a much lower stretch ratio such as of the order of 0.5 or even 0.3, the speed of spinnin must be reduced to about yards per minute.

The high elongation yarns of this invention differ from conventional yarns. Figure 1 is a cross-section of a regular 55 denier-18 filament cellulose acetate yarn, and Figure 2 is a crosssection of a 55 denier-18 filament high elongation yarn produced by the process of this invention. From a comparison of the figures, it can be seen that the yarns of this invention are more crenulated than the yarns produced by the normal spinning processes. The greater crenulated nature of the yarns of this invention is desirable because the yarns have greater covering power and fabrics made therefrom are more uniform in appearance.

The high resistance to abrasion and the high 3 impact strength of the yarns of this invention make them useful where the conventional yarns could not be used satisfactorily. For example, the high elongation yarns of this invention are advantageous in certain specific uses such as in carpet pile yarns and in military cargo,- chutes. In comparing satins' prepared from conventional control yarns and from high elongation yarns of c this invention, it was found that the yarns hay-- ing about 35% greater elongation over the control yarn, gave fabrics which had:

16% higher dry grab strength 19% higher wet grab strength 58% higher dry grab elongation 44% higher wet grab elongation 66% higher trapezoid tear strength 7 higher tongue tear strength 7% higher Mullen bursting strength higher Taber abrasion resistance yarns of, this invention did not delusterupon being boiled as much as did conventional fabrics; These advantages may be obtained without sacrifice in mill processing.

It is to be understood, of course, that the above description is for the purpose of" illustration only and that my invention is not limited to the exact conditions herein set out but is subject rather to all variations and modifications falling within the terms and spirit thereof as defined in the following claims;

I claim:

1'. In a process for spinning cellulose acetate filaments by extruding a spinning solution of said cellulose acetate, the improvement comprising extruding said solution, containing about 25% of said cellulose acetate and being heated to a temperature of about C. to about 82 0., at a rate-cf about 700 yardsiper minuteand winding the resultant, filaments at: a speed of about 608 yards per minute, the ratio of said winding to said extruding being about 0.85.

2. In a process for spinning cellulose acetate filamentsby extruding a spinning solution of said cellulose acetate,, the. steps which comprise extrudingsaid; solution at a temperature of about 75 C..'tw ahoutzfifi? C. and at a rate exceeding 600 yards per. minute jet velocity and winding the resultant filaments at a speed greater than 500; yards per minute but less than said rate of extrusion, the ratio of said winding to said jet velocity being. about 0.85.

3; In a process for spinning cellulose acetate filaments by extruding a spinning solution of said cellulose acetate, the steps which comprise extrudingl said solution at. a temperature, of about 7.5 C2. to about 85? C" through aspinneret. having relatively smallholes saicl'. solution having a relatively high viscosity ofi about 300- to about 400 poises measured atv 25% concentration and 409 (1. and said extruding being at a. rate exceeding 600 yards per. minute jet velocity and winding the, resultant filaments at a speed greater than 50h yards per minute but less than the rate of extrusion, the. ratio of said winding to said jet velocity being about 0.85.

ALBERT J. JR.

REFERENCES CITED The following references are of record in the file of this. patent;

STATES PATENTS Number Name Date 2,249,745 Charch et al. July 22, 1941 2,290,929 'Whitehead' July 28,, 1942 2,366,278 Mehler, Jr Jan. 2, 1945 2, 38 '7','.791' Hofiman Oct. 30', 1945 2,431,435. Taylor Nov. 25, 194'! 

1. IN A PROCESS FOR SPINNING CELLULOSE ACETATE FILAMENTS BY EXTRUDING A SPINNING SOLUTION OF SAID CELLULOSE ACETATE, THE IMPROVEMENT COMPRISING EXTRUDING SAID SOLUTION, CONTAINING ABOUT 25% OF SAID CELLULOSE ACETATE AND BEING HEATED TO A TEMPERATURE OF ABOUT 80* C. TO ABOUT 82* C., AT A RATE OF ABOUT 700 YARDS PER MINUTE AND WINDING THE RESULTANT FILAMENTS AT A SPEED OF ABOUT 608 YARDS PER MIMUTE, THE RATIO OF SAID WINDING TO SAID EXTRUDING BEING ABOUT 0.85. 